The present invention relates generally to a fiber opening device having a combing roller encased by a casing in an open-end spinning unit, more specifically to a structure according to which a wear-resistant member is provided at edges of apertures formed in said casing and communicating with the fiber transferring passage formed by and between said combing roller and said casing.
In most designs of fiber opening devices in open-end spinning units, the casings are usually made of aluminium diecastings. It has been known that the casing which is made of such comparatively soft material tends to allow development of rapid wear or bruises on the surfaces which are always subjected to contact with fibers or trash contained therein. The tendency of such wear or bruises is more remarkable at the edge portion formed downstream (with respect to the direction of fiber transferring) of the trash outlet port which is exposed to impingement action of the trash during spinning operation. The same tendency can be found at the edge portion provided at the mouth of the fiber supplying channel for peeling off the fibers from the combing roller.
If the edge portion of any aperture which is formed on the inner wall surface of the casing in the fiber opening device is worn and bruised, the flow of fibers through the fiber transferring passage is restricted by such flawed edge. Namely, those fibers which are caught by such edge act to hinder the flow or passage of the subsequent fibers, with the result that slubs are formed in the spun yarn and the yarn thus formed is rendered inevitably uneven in strength, thus causing serious deterioration to the spun yarn quality.
In order to solve the above problem, it has been contemplated heretofore that a wear-resistant ring, e.g. a ring made of steel, should be inserted in the casing.
To describe briefly the manner in which the fibers are moved in the opening device of a spinning unit, the fibers in the form of sliver are fed by the coacting feed roller and presser into the fiber transferring passage formed between the combing roller and the casing. In this passage, the fibers are transferred while being combed or opened-up by the rotating combing roller to the fiber feed channel, through which they are supplied to the spinning rotor.
The casing of such fiber opening device is formed with apertures as the trash receiving outlet port and fiber feeding channel, both of which are in communication with said fiber transferring passage and face the combing roller. In such structure of the casing, the edge on the downstream side of the trash outlet port and the fiber peeling edge of fiber feeding channel are placed under the influence of impinging pressure or impact exerted by the trash and fibers. Therefore, these edges in particular are susceptible to rapid wear and harmful bruises. In an attempt to avoid the development of such wear and bruises, the use of a wear-resistant ring on the inner wall surface of the casing has been proposed. Such a ring has been formed therein with apertures or openings which are adapted to match the corresponding ports formed on the inner wall surface of the casing, namely the trash outlet port, fiber feeding channel port, and the fiber entrance port adjacent the feed roller, respectively. However, it is extremely difficult to install such a ring within the casing in accurately-aligned relation thereto, as well as to manufacture the ring to such a tolerance that the mating apertures may match accurately to each other. Moreover, since the fiber opening device is always placed under the influence of constant vibration produced by the combing roller which rotates at a high speed, there is a fear that the ring may be loosened and slipped off a casing. Because the ring which is once removed in such a way receives serious flaws or deformation, it cannot be reused. Re-manufacturing of a new ring is costly, and the subsequent re-installation of the new ring calls for laborious procedures.